[R] how to perform multiple comparison？

Jim Lemon drjimlemon at gmail.com
Fri May 20 02:19:00 CEST 2016

```Hi laomeng_3,
Have a look at the padjust function (stats).

Jim

On Fri, May 20, 2016 at 1:56 AM, laomeng_3 <laomeng_3 at 163.com> wrote:
> Hi all:
> As to the anova, we can perform multiple comparison via TukeyHSD.
> But as to chi-square test for frequency table,how to perform multiple comparison?
>
> For example, if I want to compare 3 samples' ratio(the data has 3 rows,each row corresponds to 1 sample,and has 2 columns,each column corresponds to positive and negative respectively).
>
>
> dat<-matrix(c(6,30,8,23,14,3),nrow=3)
> dat
>       [,1] [,2]
> [1,]    6   23
> [2,]   30   14
> [3,]    8    3
>
>
>
> chisq.test(dat)
>
>        Pearson's Chi-squared test
>
> data:  dat
> X-squared = 17.9066, df = 2, p-value = 0.0001293
>
>
> The result shows that the difference between the 3 samples is significant.But if I want to perform multiple comparison to find out which pair of samples is  significantly different,which function should be used?
>
>
> Many thanks for your help.
>
> My best
>
>
>
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